The long-term objectives of this basic research are to specify the distinctive acoustic patterns in speech signals that perceptually differentiate the vowels and consonants of different languages and to explore the nature of both language-universal and language-specific perceptual processes by which adult listeners recover the linguistic message from the complex acoustic signal. Three sets of experiments are proposed. A) Acoustic and perceptual studies of the role of dynamic (time-varying) acoustic information in the specification of German vowels produced in continuous speech will investigate similarities and differences in the acoustics and perception of North German (NG) and American English (AE)A vowels by native speakers. B) Studies of the perceptual similarities of native-language and non-native vowels and consonants will examine how subjects judge the goodness-of-fit of non- active phonetic segments to native categories (cross-language similarities) and how non-native listeners differ from native listeners in their perceptual similarity judgments of selected sets of vowels and consonants (within-language similarities). The vowel inventories of NG, Japanese (J), and AE will be compared. In addition, AE and J listeners' judgments of AE approximant consonants/r, 1, w, j/and AE listeners' judgment of Hindi stop consonants will be examined. C) Perceptual training studies will attempt to improve adult listeners' perception of non-active vowels and consonants. English speakers will be trained on NG vowels and Hindi stop consonants; Japanese speakers will be trained on AE vowels and approximant consonants. Results of these studies will provide a better understanding of the role that linguistic experience plays in the modification of perceptual processes. In addition, they contribute information which may be valuable in improving the teaching of foreign languages to adults and in the amelioration of perceptual problems in children and adults with speech disorders.